Field
The invention relates generally to a polyaxial bone anchoring device and an instrument for use with the device. More specifically, the bone anchoring device includes a receiving part for coupling a rod to a bone anchoring element, wherein the receiving part has a rod receiving portion for receiving the rod and a head receiving portion for clamping a head of the bone anchoring element, and a locking ring for locking the head in the head receiving portion. The receiving part and the locking ring are configured to be movable relative to each other from a non locking position to a locking position, and vice versa, for example, by using an instrument.
Description of Related Art
US 2011/0276098 A1 describes a polyaxial bone anchoring device including a receiving part for receiving a rod for coupling the rod to a bone anchoring element, the receiving part including a rod receiving portion with a channel for receiving a rod and a head receiving portion that is flexible for clamping a head of the bone anchoring element. A locking ring is configured to be positioned around the head receiving portion. The locking ring can assume a first position where the head receiving portion is expandable to facilitate insertion of the head and a second position in which the locking ring compresses the head receiving portion such that the head is held adjustably at a first angular position relative to the receiving part. Further, the locking ring can assume a third position in which the head is locked in the receiving part. For locking the head, a locking element is used that also locks the rod in the rod receiving portion.
US 2013/0085536 A1 describes a polyaxial bone anchoring device including a receiving part with a rod receiving portion and head receiving portion for introducing and clamping of the head and a locking ring configured to be arranged around the head receiving portion. The locking ring includes an engagement structure for engagement with a tool to allow the locking ring to be moved out of the locking position, i.e. releasing the locking mechanism. This enables a surgeon or other practitioner to carry out revisions or further positioning or re-positioning of the angular position of a receiving part with respect to the bone anchoring element.